Sound Transit boasts about creating the first “100% carbon-free light rail service” in the nation. Yet when the contractors build concrete columns and stations, they burn fossil fuels that reduce the electric trains’ net climate benefit.

In a tiny experiment to limit greenhouse gas, crews building the north half of Sound Transit’s 2024 Northgate-to-Lynnwood extension are fueling two forklifts and a dirt loader in Mountlake Terrace with renewable plant-based diesel. It performs as well as petroleum, the crew says.

The test by Skanska USA reflects worldwide attention by the contracting and engineering industries on reducing “embodied carbon,” which refers to sources like concrete-making, heavy equipment and supply chains, as opposed to carbon the driving public spews from our tailpipes.